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Cytologic evaluation of the urinary tract can be diagnostically rewarding in cases of renomegaly or when discrete kidney or bladder masses are identified. Cytology can often help to distinguish between cystic, inflammatory, and neoplastic disorders. Various types of cystic and benign urinary tract lesions, diseases associated with urinary tract inflammation, and the cytologic differences between primary and metastatic neoplasms of the kidney and bladder are described. Basic sampling techniques for urinary tract cytology are also discussed., (Copyright © 2018 Elsevier Inc. All rights reserved.)

A complete urinalysis is an essential diagnostic test to perform in veterinary patients. When interpreted in the context of a patient's clinical history, physical examination findings, and other diagnostic test results, a urine specific gravity, chemical analysis (often via semiquantitative dipstrip testing), and sediment examination are vital to detect both renal and nonrenal disorders. In this article, we describe the usefulness of each component of a urinalysis, the significance of and how to interpret results, and common causes of false-negative and false-positive results., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Proteinuria is a negative prognostic indicator for dogs and cats with chronic kidney disease. A normal dog or cat should excrete very little protein and have a urine protein:creatinine ratio that is less than 0.4 or less than 0.2, respectively; persistent proteinuria above this magnitude warrants attention. Administration of angiotensin converting enzyme inhibitors and/or angiotensin receptor blockers, blood pressure control and nutritional modification are considered a standard of care for renal proteinuria. Renal biopsy and administration of immunosuppressive agents should be considered in animals with glomerular proteinuria that have not responded to standard therapy. Targeted patient monitoring is essential when instituting management of proteinuria., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Routine monitoring of clinicopathologic data is a critical component in the management of older patients because blood and urine testing allows the veterinarian to monitor trends in laboratory parameters, which may be the early indicators of disease. Laboratory profiling often provides an objective and sensitive indicator of developing disease before obvious clinical signs or physical examination abnormalities are observed. The primary key to the power of this evaluation is that the data are collected year after year during wellness checks and are examined serially. Chronic renal failure, chronic active hepatitis, canine hyperadrenocorticism, diabetes mellitus, and feline hyperthyroidism were reviewed and expected laboratory findings are summarized.

This article discusses the 2007 recall of canned pet food because of concerns about adverse effects on kidney function of cats and dogs. The discovery of melamine and cyanuric acid in the foods is detailed. Case studies, including clinical, pathology, histology, and toxicology findings, are presented. An attempt is being made to identify the minerals in the uroliths and kidney tissues of affected animals.

Urine chemical analysis can extend "beyond the dipstick" with an understanding of renal physiology and expected changes in electrolyte and solute handling. Urine electrolytes, such as sodium and chloride, can be helpful in discerning prerenal azotemia from acute renal tubular damage, which occur secondary to nephrotoxins or ischemia. Urine osmolality also is essential in determining appropriate antidiuretic hormone action and renal water handling. Urine solutes, such as albumin and brush border enzymes, may be more sensitive than plasma markers for early renal dysfunction. This article reviews these topics and the use of "extended" urine indices in veterinary medicine.

Proteinuria is a common disorder in dogs and cats that can indicate the presence of chronic kidney disease (CKD) before the onset of azotemia or the presence of more severe CKD after the onset of azotemia. Although a direct pathogenetic link between glomerular disease, proteinuria, and progressive renal damage has not been established, attenuation of proteinuria has been associated with decreased renal functional decline in several studies. There is a need to continue to increase our understanding of the effects of proteinuria on the glomerulus, the tubule, and the interstitium in dogs and cats.

Protein-losing glomerulonephropathy can be a challenging disease for veterinarians to manage. This case-based article illustrates long-term management of protein-losing glomerulonephritis in a dog. Prolonged survival of this patient was attributed to early diagnosis and carefully planned therapeutic intervention consisting of dietary protein reduction and modulation of blood pressure with angiotensin converting enzyme inhibition.

Medical therapy is an effective method of canine struvite urolith dissolution. Recommendations include (1) eradication or control of urinary tract infection (if present), (2) use of calculolytic diets, and (3) administration of urease inhibitors to patients with persistent urinary tract infection caused by urease-producing microbes.

Urine must be oversaturated with magnesium ammonium phosphate for struvite uroliths to form. Oversaturation of urine with magnesium ammonium phosphate may be associated with several factors, including urinary tract infections with urease-producing microbes, alkaline urine, diet, and genetic predisposition. Of the urease-producing microbes, staphylococci are most struvitogenic in dogs. The precise mechanisms resulting in formation of sterile struvite uroliths in dogs have not been determined.

This article discusses techniques of bacterial culture of uroliths, interpretation of results of culture, and antimicrobial therapy of bacteria associated with uroliths.

Distal RTA is characterized by decreased distal renal tubular hydrogen ion secretion, decreased ability to acidify urine, hypercalciuria, hyperphosphaturia, hypocitraturia, and metabolic acidosis. Because of the resulting alterations in urine composition and pH, patients with distal RTA are predisposed to urolithiasis and renal calcification. Diagnosis of distal RTA is important because it is a potentially reversible disorder that, left untreated, may cause nephrocalcinosis, recurrent urolith formation, moderate to severe metabolic acidosis, and renal failure.

Uroliths composed primarily of calcium phosphate are identified in approximately 3 per cent of canine stone patients. Predisposing factors to the formation of calcium phosphate uroliths include elevated urine pH, hypercalciuria, and the presence of crystallization inhibitors and promoters. Medical therapy of patients forming calcium phosphate uroliths should initially be directed at removing factors contributing to urine supersaturation with calcium phosphate.

This article contains an analysis of data compiled from 813 specimens of canine uroliths submitted to the Urinary Stone Analysis Laboratory at University of California School of Veterinary Medicine.

Crystalluria results from oversaturation of urine with crystallogenic substance. However, oversaturation may occur as a result of in vitro as well as in vivo events. The microscopic appearance of crystals only represents a tentative identification of their composition because variable conditions associated with their formation, growth, and dissolution may alter their appearance. Definitive identification is dependent on physical methods such as optical crystallography, x-ray diffraction, and electron microscopic analysis.

A study was performed to compare qualitative test results of canine uroliths with quantitative test results. Qualitative test results were in agreement with quantitative test results in only 96 of 223 specimens (43 per cent). Lack of agreement was caused by false-negative qualitative test results (85 of 223), false-positive qualitative test results (15 of 233), and a combination of false-negative and false-positive qualitative test results (27 of 233). This study indicates that the veterinary profession should abandon exclusive use of qualitative chemical test kits for uroliths.

Urinary tract infection should be considered in a differential diagnosis on the basis of history, physical examination, and urinalysis. To definitively diagnose urinary tract infection, significant bacteriuria must be found by quantitative bacterial culture. The absolute definition of significant numbers of bacteria varies with the method of collection because of the possibility of contamination with the normal bacterial flora of the lower genitourinary tract. Numbers of bacteria are also influenced by the manner in which urine samples are handled, by urine concentration, and by frequency of voiding. Quantitative and qualitative urine cultures should also be used to monitor the efficacy of treatment in chronic and recurrent infections. Cultures should be repeated three to five days after the termination of antimicrobial therapy to ensure elimination of infection. If feasible, cultures should also be repeated two to three days after begining therapy to ensure the antimicrobial agent selected is effective. Remission of clinical signs should not be used to judge efficacy of treatment, especially in chronic or recurrent infections, since infections can persist without causing clinical signs, particularly if bacterial numbers are temporarily reduced. Determination of the minimum inhibitory concentration of an antibiotic for a particular bacteria is preferable to Kirby-Bauer antibiotic sensitivity testing in urinary tract infection because of the difference in serum and urine concentrations of most antibiotics. Bacteria are not sensitive or resistant to an antibiotic but rather to a concentration of that antibiotic. If Kirby-Bauer sensitivity testing is used for urinary tract infection, results must be interpreted carefully since drugs reported as ineffective may be effective in vivo.

Metabolic disorders, medication, and diagnostic agents may be associated with urolithiasis in dogs. Examples of uroliths that have been uncommonly encountered in dogs include xanthine, dolomite, tetracycline, and sulfonamides. Detection of these and other apparently uncommon uroliths requires a high index of suspicion and proper methods of analysis.

The etiopathogenesis of uric acid, sodium acid urate, and ammonium acid urate uroliths in non-Dalmatian dogs appears to be a complex phenomenon. It may involve one or more pathologic and/or physiologic processes acting independently or in concert to increase urinary concentration of lithogenic substances that result in initiation, growth, and retention of urate uroliths. Increased urine uric acid concentration and/or urinary excretion of uric acid appear to be primary predisposing factors in urate lithogenesis. Specific disorders resulting in hyperuricuria may involve abnormalities of increased synthesis, diminished biodegradation, and/or enhance excretion of uric acid. In addition, ammonium ion, hydrogen ion, and other organic and inorganic urine constituents appear to have major influences on urate urolith formation. Unfortunately, many specific disorders of uric acid metabolism and other factors promoting or inhibiting urate urolith formation remain poorly characterized in the majority of non-Dalmatian dogs with urate urolithiasis. Growing awareness of the significance of urate uroliths in non-Dalmatian dogs should encourage further investigation into the identification, characterization, and quantitation of parameters influencing urate lithogenesis. Results of such studies are required for development of practical and effective strategies for treatment and prevention of canine urate urolithiasis.

Homozygosity for a defective recessive gene results in all Dalmatians having elevated concentrations of urine uric acid and predisposes them to formation of purine uroliths. Why some animals form uroliths and others do not is not known. In a pilot breeding experiment, the incidence of sensorineural deafness among backcrossed, high urine uric acid Dalmatians was significantly higher (probability less than 0.05) than among low urine uric acid siblings. Urine uric acid values for Dalmatians reported in the literature are not likely to be comparable, because uric acid appears to be more likely to precipitate in Dalmatian urine than in the urine of other dogs and man. Heating, alkalinization, and thorough mixing are required whenever specimens are transferred from one container to another or an aliquot is removed for assay.

Macroscopic examination of urine is an integral part of urinalysis, and blood and bile pigments are a common cause of abnormal coloration. Urine SG is a convenient index of urine concentration and should be correlated with the patient's hydration status to determine the ability of the kidneys to concentrate and dilute urine. The pH of urine of dogs and cats normally is dietary dependent, but alkaline urine may suggest that the urinary tract is infected with a urea splitting organism. The dipstick test for proteinuria is convenient but less reliable than the sulfosalicylic acid method. The dipstick test for blood should not be used as a substitute for microscopic examination of urine but is of value in detecting hemoglobinuria and myoglobinuria, when red cells may be absent in the sediment. The finding of glucose, ketones, and bilirubin in urine, when interpreted properly, may indicate the presence of disease processes not associated with the urogenital tract. Microscopic examination of urine sediment must be interpreted in combination with the physical and chemical composition of urine, but excessive numbers of cells, casts, crystals, and bacteria may provide evidence of disease. The absence of these structures in the sediment, however, does not eliminate the possibility of disease. The ability of the kidneys to concentrate urine is dependent on normal kidney function and the production and release of ADH. A urine SG greater than 1.030 in dogs and 1.035 in cats indicates that the functions associated with concentrating urine are adequate. In the evaluation of the patient's ability to form concentrated urine, the status of hydration must be considered; this may require water deprivation tests or administration of ADH. The estimation of blood urea nitrogen concentration, with the use of test strips, may provide a convenient but not specific measure of renal function.

Medical therapy that may be effective in promoting dissolution of canine ammonium urate uroliths includes the following: reduction of dietary purines, reduction in in vivo production of uric acid, and alkalinization of urine.

Cystine uroliths form as a result of a complex metabolic disturbance in amino acid metabolism and transport. The inheritance of this disease is obscure because it does not follow a standard mendelian pattern. Uroliths are a vexing clinical problem because the recurrence rate is high. Accurate diagnosis of uroliths requires use of crystallographic methods. The renal defect leading to excessive excretion of cystine is variable. The only effective method of prevention of recurrence is use of D-penicillamine, which is poorly tolerated by some dogs.